The subject of this invention is a device designed for regenerating the human dermis. It also concerns a process for producing such a device.
Human dermis regeneration using a collagen or equivalent matrix followed by an epidermal graft is one of the most commonly used techniques for skin reformation. Third-degree burns are one of the main indications for this technique. Dermal regeneration is also called for in plastic surgery for the treatment of keloids, retractile scars, scar plaques, hypertrophic scars, skin necrosis following rejection of a skin graft and nevus. Dermal regeneration is also called for after the excision of a skin tumor, for the treatment of chronic or acute wounds when the dermis needs to be regenerated and in traumatology for reconstructive surgery.
Document U.S. Pat. No. 4,060,081 describes a device for dermal regeneration of the type described in the invention, in the form of a multilayer complex combining, successively:                an absorbable polymeric matrix designed to come into contact with muscle or subcutaneous tissue, depending on the indication;        a textile mesh with unspecified characteristics, applied to the surface of the matrix, not in contact with the muscle or subcutaneous tissue;        a permeable film used as a temporary skin substitute, applied in strips directly onto the textile mesh.        
The complex is thus presented in the form of three separate layers, respectively:                an absorbable polymeric matrix;        a textile mesh;        a transparent, permeable layer, in practice in the form of a silicone film.        
When these multilayer complexes are used for dermal regeneration, notably in burn victims, the surgeon proceeds as follows.
Firstly, if necessary, the nonviable parts of the burnt dermis are excised to obtain viable underlying tissue.
Directly on the muscle, or depending on the case, on the subcutaneous tissue:                the multilayer complex is positioned so that the absorbable polymeric matrix is in contact with the muscle or subcutaneous tissue;        the device is then attached to the muscle or cutaneous tissue using staples or suture, to keep it from moving during the dermal regeneration phase and to keep the wound sealed;        once the dermis has been regenerated, which may take approximately three weeks, the double transparent film/textile mesh layer is removed;        then, in the last step, an epidermal graft is performed on the regenerated dermis.        
One of the major disadvantages of the device described in document U.S. Pat. No. 4,060,081 is that there is a direct contact between the dermis that is being formed and the textile mesh. When the double permeable film/textile mesh layer is removed, two situations may occur.
In some cases, removing the film/textile mesh group can cause at least part of the reformed dermis to pull off due to colonization of the textile by the host cells. Bleeding is then possible, as well as irregularity in the dermis. The epidermal graft is thus performed on a non-homogenous dermis with risks of persistent skin defects after reconstruction.
In other cases, the film can come unattached from the mesh so that the mesh remains set in the dermis being formed. In this hypothesis, the epidermal graft will be performed on a dermis containing a useless, non-absorbable material with risks of losing skin functions in terms of suppleness, elasticity and esthetics due to the persistence of the textile structure.
Another disadvantage of the device in the prior art is that it causes the formation of tears in the transparent film and the collagen matrix during attachment with staples and during regeneration of the dermis. The tear in the collagen matrix then leaves a hole that will have to be filled by the formation of a tissue called “granulation tissue”, which is a sign of poor dermal reconstruction.
A third disadvantage lies in that the permeable film, given how thin it is, can tear near the points of attachment under the effects of the patient's movement. In this case, the subcutaneous tissue or muscle is no longer isolated from the ambient air, providing an open door to a major risk of contamination.
A fourth disadvantage lies in that the textile mesh gives the device a certain degree of stiffness. It may no longer adapt to the wound being treated on certain parts of the body with pronounced relief such as the fingers or face. Contact between the polymeric material and the bed of the wound is indispensable for good dermal reconstruction.
Lastly, the transparency of the permeable film can be affected by the presence of the textile mesh. Transparency is indispensable for monitoring the wound and notably for verifying that there is no infection or hematoma which could lead to the failure of dermal regeneration. Transparency also makes it possible to verify the progress made in dermal regeneration in order to schedule the epidermal graft.